The invention relates to utility knives, and more particularly, utility knives adapted to be conveniently used with tape measures.
Utility knives are well known in the art and used for a wide variety of cutting needs. In general, a utility knife includes a handle and a removable cutting blade. Utility knife handles have been constructed in a number of different shapes, most shapes being generally designed to fit comfortably in the hand during cutting. The handles generally include a 2-part housing which is held together with screws and which contains a hook for removably inserting a blade. The blades are either fixed in a position partly extending from the handle, or may be retracted into the handle from an extended position. In using the utility knife for cutting, the user grasps the knife in one hand, applies the cutting edge of the blade to the material to be cut, then applies simultaneous drawing and pushing forces on the blade.
In some applications, the cuts from the utility knife must be precisely placed. For instance, plasterboard (also known as drywall or sheetrock) is a common wall material that is generally sold in sheets sized 4 feet by 8 feet. When attaching these sheets to studs to form a wall, it is often necessary to cut a strip off the side of the plasterboard sheet, for example, for installation in a corner of a room or to form a soffit. Also, quite often, the space in which the plasterboard is to be applied is irregular in shape, requiring difficult and precise cuts for optimal area coverage. A skilled user conventionally makes such cuts by simultaneously operating a tape measure along with the knife.
For instance, when cutting plasterboard using conventional means, the user holds the tab of a tape measure against the handle of the utility knife with his or her thumb, as close to the surface to be cut as possible. The user then extends the tape measure across the plasterboard sheet to the desired distance with the opposite hand. Then, with the tape measure reel in one hand and the knife and tape measure tab in the other, the user will simultaneously slide both the knife and the measuring tape down the sheet to score a line in the plasterboard. The tape measure is then set aside, and a deeper final cut is made along the score line. The strip to be removed is then bent with respect to the remainder of the sheet until it snaps.
This method suffers from a number of drawbacks, however. Because it is difficult to apply sufficient pressure to the knife while holding the tape measure, the user must make two cuts in the plasterboard; if the user presses too hard during the first cut, there is a risk of injury and that an inaccurate cut will be made. Thus, the first cut is generally not sufficiently deep for performing the function of creating a score deep enough for bending the plasterboard, and a second cut is generally needed. Also, when measuring and scoring, the measurement is inaccurate by the distance between the knife blade and the end of the ruler, which must be estimated and accounted for by the user. In addition, the tape measure tab is awkward and uncomfortable to grasp during cutting. Also, if the tape measure tab slips from the user""s grasp during cutting and the tension between the blade and the measure is changed, the blade will generally deflected from its desired course and create inaccurate or jagged cuts. Lastly, placing one""s thumb so near the cutting surface of the blade during operation of the knife subjects the user to unnecessary levels of risk of cutting the fingers.
Several prior art inventions attempted to overcome these risks. One such invention is a utility knife attachment that creates a slot next to the blade whereby the tab from a utility knife may be attached. This invention, however, is attached next to the blade and limits the depth to which the blade may be used for cutting, since materials other than plasterboard, such as foam insulation, are also cut by utility knives. In addition, it is necessary to carry a small part in addition to the utility knife. Lastly, in order to install and remove the part, the utility knife must be disassembled. Another prior art device includes a slot for receiving a tape measure tab that is formed in the backbone of a utility knife, wherein the tape measure is held parallel to the cutting edge of the blade of the utility knife. This device creates cuts that are inaccurate in that the measure is held away from the wall and almost perpendicular to the wall, causing the user to estimate and account for these inherent inaccuracies in measurement. Moreover, where the rule surface of the measure is not parallel to the surface to be cut, the rule may be difficult to read, leading to mistakes in measurement.
Thus, it is a principal object of the invention to provide a utility knife which is capable of cooperating with a tape measure to allow the cutting blade to be positioned accurately.
It is another object of the invention to provide a means for simultaneous cutting with a utility knife and accurate measuring which will allow the user the user to keep his fingers away from the blade.
It is yet another object of the invention to provide a convenient means for simultaneous cutting of plasterboard and measuring with a tape measure.
It is also an object of the invention to provide a means for simultaneous measuring and cutting where the rule surface of the measure remains parallel to the surface of the material to be cut.
Other objects and variations of the invention will be obvious to those skilled in the art and are included within the scope of the invention.
The present invention overcomes the drawbacks in the prior art by incorporating a pair of hooks into the blade end of the handle of a common utility knife, which hooks are designed to removably secure the tab of a spring-biased measuring tape such that the tape may extend roughly laterally from the knife but also roughly parallel to the surface being cut.
The angles of the hook are designed to correct for measuring inaccuracies created by the distance that the knife blade must be held away from the surface to be cut; the invention allows the printed measuring surface of the tape measure to remain roughly parallel to the surface being cut, allowing for great ease in reading measurements from the ruler during cutting. The positioning of the hooks near the bottom surface of the knife and very close to the end of the knife allows for the tape to be in very close proximity and parallel orientation to the surface to be cut, thus improving the visibility of the measuring surface and the accuracy of the measurement over prior art devices. In addition, the hooks minimize the need for the user to place his fingers alongside the cutting surface of the blade. Also, the hook of the invention allows the blade to be inserted to its full depth. Lastly, the utility knife of the invention distributes the pulling forces created by extending the tape measure during cutting evenly throughout the housing than would be obtained by a device which attaches to a blade.
Although the angled hooks may be formed in a variety of locations or in a variety of configurations, the preferred embodiment of the present invention employs a generally inverted triangular hook formed in the bottom surface of both halves of the housing. Positioned thusly, the user may comfortably grasp the handle of the knife in a natural manner while the measuring tape remains close to the surface to be measured, and the rule remains approximately parallel to the surface to be measured and thus clearly visible to the user. In addition, this position will not interfere with the retraction mechanism of a retractable utility knife.
The hook may be sized to accommodate almost all commercially available tape measure tabs which are inserted and removed with a simple sliding action, thus creating a fast and smooth use.
Although the preferred embodiment will be set forth in greater detail below, other features and embodiments will the obvious to one skilled in the art. Such features and embodiments are within the scope of this invention.